1 /* 2 * Memory preserving reboot related code. 3 * 4 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com) 5 * Copyright (C) IBM Corporation, 2004. All rights reserved 6 */ 7 8 #include <linux/errno.h> 9 #include <linux/highmem.h> 10 #include <linux/crash_dump.h> 11 12 #include <asm/uaccess.h> 13 14 static void *kdump_buf_page; 15 16 /** 17 * copy_oldmem_page - copy one page from "oldmem" 18 * @pfn: page frame number to be copied 19 * @buf: target memory address for the copy; this can be in kernel address 20 * space or user address space (see @userbuf) 21 * @csize: number of bytes to copy 22 * @offset: offset in bytes into the page (based on pfn) to begin the copy 23 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 24 * otherwise @buf is in kernel address space, use memcpy(). 25 * 26 * Copy a page from "oldmem". For this page, there is no pte mapped 27 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 28 * 29 * Calling copy_to_user() in atomic context is not desirable. Hence first 30 * copying the data to a pre-allocated kernel page and then copying to user 31 * space in non-atomic context. 32 */ 33 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, 34 size_t csize, unsigned long offset, int userbuf) 35 { 36 void *vaddr; 37 38 if (!csize) 39 return 0; 40 41 vaddr = kmap_atomic_pfn(pfn, KM_PTE0); 42 43 if (!userbuf) { 44 memcpy(buf, (vaddr + offset), csize); 45 kunmap_atomic(vaddr, KM_PTE0); 46 } else { 47 if (!kdump_buf_page) { 48 printk(KERN_WARNING "Kdump: Kdump buffer page not" 49 " allocated\n"); 50 kunmap_atomic(vaddr, KM_PTE0); 51 return -EFAULT; 52 } 53 copy_page(kdump_buf_page, vaddr); 54 kunmap_atomic(vaddr, KM_PTE0); 55 if (copy_to_user(buf, (kdump_buf_page + offset), csize)) 56 return -EFAULT; 57 } 58 59 return csize; 60 } 61 62 static int __init kdump_buf_page_init(void) 63 { 64 int ret = 0; 65 66 kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL); 67 if (!kdump_buf_page) { 68 printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer" 69 " page\n"); 70 ret = -ENOMEM; 71 } 72 73 return ret; 74 } 75 arch_initcall(kdump_buf_page_init); 76